1. Field of the Invention
The present invention relates to an image advertising system, and more particularly, to an image advertising system having minimal size and weight and a triangular structure capable of guaranteeing a sufficient viewing angle and a sufficient large screen, and to allow people to watch images in multi directions.
In detail, the present invention relates to an image viewing system, in which projection light paths of plural projectors cross one another, images are formed in a minimal sized image case in multiple directions, capable of being installed to a wall or a safety fence of a subway station, and capable of being engaged with a trailer to be conveniently moved.
2. Description of the Related Art
FIG. 9a is a view illustrating a conventional image viewing system including a screen 1e installed to a wall and a projector 2 for projecting an image upon the screen 1e or including a single flat-screen display such as a plasma display panel installed to a wall in the horizontal direction.
Generally, a viewing range within which a viewer 12 may effectively view an image, i.e. a horizontal length A of the screen 1e, as shown in FIG. 9, is about 30 degrees outward from the both vertical edges of the screen 1e, i.e. 60 degrees. A viewer must be within these 60 degrees to effectively view the entirety of the screen 1e. This fact is already known.
For reference, as shown in FIG. 1a, a horizontal length A to a vertical length B, e.g. the aspect ratio, is 16:9, i.e. A:B is 1.77:1. The ratio of in a movie theater is 2.35:1.
As shown in FIG. 2, when the image is projected by the projector 2, a projection ratio of the horizontal length A of the screen 1e to a projection distance C of a standard projection lens of the projector 2, i.e. an image projection ratio (hereinafter referred to as a projection ratio), is 1:1.3, as is also already known.
Although the projection ratio of the projection lens of the projector 2 from 1:0.8 to 1:3 can be applied to the present invention, the projection ratio of the projector 2, for the purpose of illustration, is assumed to be that of the projection ratio of a standard projection lens, 1:1.3.
This means that when the projection distance C is 1.3 m, the horizontal length of the screen is 1 m and the projection distance C is longer than the horizontal length A of the screen. In other words, it means that the projection distance C of the projector 2 is equal to the length of a side of an image case 3.
In the present invention, the size of the displayed image, i.e. the horizontal length A of the screen, ranges from 0.7 m to 3 m, preferably 1.5 m. For the purpose of illustration, hereinafter, a screen having a horizontal length A of 1.5 m is described.
When the horizontal length A of the screen is 1.5 m, the projection distance C must be 1.95 (m1.5 m×1.3) due to the projection ratio 1:1.3.
As shown in FIG. 2b, by setting the projection distance C (1.95 m) of right, left, front, and rear projectors 2a, 2b, 2c, and 2d to a reference, the projection distance C of the projector 2 becomes a factor to determine the sizes of front, rear, right, and left sides of a conventional rectangular image case 10. For example, the lengths C2 of the right and left sides of the conventional rectangular image case 10 become the sum of the projection distances of the front and rear projectors 2a and 2b, C+C, i.e. 1.95 m+1.95 m=3.9 m.
Thus, the size of the conventional rectangular image case 10 determined by the front, rear, right, and left sides thereof becomes C2×C2=3.9 m×3.9 m, and the horizontal length A, i.e. the size of the image, of the transparent screen 1 becomes 1.15 m. In other words, the screen size of the conventional rectangular image case 10 (1.15 m) is only 30% of the length (3.9 m) of a side of the conventional rectangular image case 10.
In other words, as shown in FIG. 2b, when a plurality of projectors 2 is installed, the length of a side of the conventional image case 10 is double that of the projection distance C, but the size of the transparent screen is not increased.
This phenomenon, as shown in FIG. 3, occurs in a triangular image case 3b. 
Thus, according to the conventional image case, as shown in FIG. 4a, when a multi-direction image viewing system is installed to the ceiling, although the size of the conventional image case 10 is increased, the horizontal length A of the screen cannot be maximized. Moreover, as shown in FIG. 5a, when the conventional triangular image case 11 is installed in a passage, since the height C4 of the triangular is high, the size of the conventional triangular image case is also increased to obstruct pedestrian passage.
Moreover, as shown in FIGS. 6a and 7a, in an image viewing system engaged with a trailer 8, the width of the image case 3 having plural transparent screens 1 installed in four directions must not be over the average width (1.7 m) of a 1 ton truck.
However, since the length of a side of the conventional image case 3 having the screens with a horizontal length A, 1.5 m, installed in multiple directions is 3.9 m, as shown in FIG. 6a, the horizontal length A of the conventional image case 3 is over the width D (1.7 m) of a vehicle and is over the width (2.5 m to 3.5 m) of a lane of a general paved road. Thus, the conventional image case 3 cannot be transported through the road.
Although there is an image vehicle in which the image case is fixed to the rear side thereof, since the image case cannot be separated from the image vehicle, each image case requires a corresponding vehicle. Moreover, since the size of the image case is restricted according to the size of the transporting vehicle, screens cannot be installed in multiple directions, but only in a single direction.
As shown in FIG. 9b, in a conventional screen advertising system installed in a station of a subway, a train, or the like, the projector 2 is installed on the ceiling, and a scattering screen 1e is installed to a wall nearby the windows of trains, opposite to the platform.
According to the conventional screen advertising system in FIG. 9b, when the trains 91 enter the subway station, the trains 91 hide the scattering screen 1e, in the case that a safety fence 14 is installed in the subway station, since the safety fence 14 is disposed between the scattering screen 1e and the projector 2, consumers cannot view the scattering screen 1e. 
Meanwhile, passengers stand in lines at the sides of doors 13a of the trains 91 and passengers in the trains 91 exit through the central area of the doors 13a. 
Thus, as shown in FIG. 9c, when the scattering screen 1e is installed to the safety fence 14, effective view range of the scattering screen 1e, as shown in FIG. 1, is 30 degrees, respectively, at the right and left sides thereof, i.e. a total of 60 degrees. Thus, as shown in FIG. 9c, since the passengers at the sides of the doors 13a cannot view the entire scattering screen 1e, but only some passengers may view, advertising impact of the conventional screen advertising system is deteriorated.
In addition, as shown in FIG. 9a, in order to increase the advertising impact of the image advertising system, the image advertising system, installed in passages such as passages in a shopping mall through which consumers walk, must have a viewing range greater than 120 degrees. However, the conventional image advertising system has a viewing range of only 60 degrees, i.e., the sum of the right and left ranges. Thus, it is an object of the present invention to increase the viewing angle.
As shown in FIGS. 3 and 16a, when the projectors 2 are disposed at the inner intermediate portion of the conventional triangular image case 11 and the transparent screens 1 are installed at the sides of the conventional triangular image case 11, since the size of the conventional image advertising system is double that of the projection distance C of the projectors and the weight is increased due to the increased size, the conventional triangular image case installed to the wall of the passage serves as a factor to disturb consumers' passing.
Thus, in the multi-direction image system using the projectors 2, there are important technical problems such that a screen having a maximal horizontal length A is implemented in an image case 3 having a minimal space, to the contrary, the same size screen is implemented in the minimal sized image case 3, and/or images are displayed in two directions, i.e. in the right and left directions of the image case 3, in three directions, i.e. in the right, left, and central directions of the image case 3, or in multiple directions, i.e. in the front, rear, right, and left direction of the image case 3.